U.S. Officials are focusing particularly on yemen this morning. Believing al qaeda operatives are already in place there and possibly other countries, as well, just waiting for the opportunity to strike. Intelligence committee member dutch ruppersberger told me on "this week," this is dead serious. Those operatives are in place because we received information that high-level people from al qaeda in the arabian peninsula ar talking about a major attack. Reporter: Communications from the al qaeda affiliate in yemen intercepted by the u.S. Revealed chilling details of a terror plot al qaeda believes is going to be big and strategically significant. I had a briefing with the vice president. It is scary. It could be a series of combined attacks so we have to be ready for everything. Reporter: Especially troubling according to one senior u.S. Official, surgically implanted devices, bombs in terrorists' body, a technique developed in yemen. "These are guys who have developed the techniques to defeat our detection methods." Which is why u.S. Officials remain vigilant here at home, as well. Because of the potential threat to airplanes, trains wherever large groups could gather. Is the threat to blow up an embassy, a consulate or something else? That part of it is unspecified but the intent seems clear. Reporter: And the intent is to what. The intent to attack western not just u.S. Interests.

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